In extrusion molding, in general, by extruding a resin material which has been melt-kneaded by means of an extruder through a resin channel formed in a channel in an extrusion die head provided at the front end part of the extruder, a molded article having a predetermined cross-sectional shape is continuously shaped. It is known that, at this time, when molding is continued for a long period of time, a deteriorated resin is adhered to the outlet of the extrusion die head (see FIG. 5 which shows the outline of one example of a conventional extrusion die head). Such an adhered matter is generally referred to as a die drool. If molding is continued with a die drool being adhered to the outlet of the extrusion die head, problems occur that the die drool is mixed in a molded article, whereby the quality of the molded article is deteriorated and traces of the die drool (die lines) are formed on the surface of the molded article in the form of a line to deteriorate the external appearance of the molded article.
In order to prevent a die drool from being formed, it is required to conduct troublesome works, i.e. to stop the molding at a predetermined interval and dismantle and clean the extrusion die head. Further, whenever the molding is stopped, the production line must be suspended, and as a result, removal of a die drool results in lowering in productivity.
Conventionally, in order to prevent generation of such a die drool, various technologies have been proposed. For example, in Patent Document 1, a nozzle piece is installed to a die plate in an exchangeable manner, and a die drool is removed together with the nozzle piece, whereby the time or cost incurred for the removal of a die drool is attempted to be reduced. In Patent Document 2, a cylindrical member having a tapered part in the inside thereof is installed to a die lip part, whereby the die drool generated in the die lip part is adhered to the tapered part and is then transferred from the die lip part to the tapered part by extrusion force, whereby the die drool is removed.